In the production of reinforced aerated concrete elements it is necessary to provide the steel reinforcements (reinforcing mats and reinforcing bodies) with a corrosion protection coating, before introduction into the viscously fluid aerated concrete. In order to apply the corrosion protection medium to the steel reinforcements, these are as a rule dipped in a bath filled with the corrosion protection medium. To hold the steel reinforcements during this dipping operation there are provided so-called support rods, of which a plurality are each fixed to a cross-piece or a frame. In dipping the steel reinforcements into the corrosion protection medium the support rods are also coated with the corrosion protection medium. After the corrosion protection medium has dried, the reinforcements can be put in the casting mould. To this end the cross-pieces are placed on the upper edge of the casting mould. The support rods now hold the steel reinforcements suspended thereon at the correct mutual spacings and spacing from the mould bottom and the sidewalls of the mould. Then the aerated concrete mass is filled into the mould. It blows up to the required height under the action of aluminium powder. After the so-called green aerated concrete block has attained sufficient strength to be transported and cut, the support rods are released from the steel reinforcements and withdrawn upwardly from the aerated concrete block by lifting the cross-pieces. Before they can be reused, cleaning of these support rods is necessary as a rule, on the one hand because they are likewise coated with the corrosion protection medium and on the other hand because inter alia aerated concrete residues adhere to the corrosion protection medium. If the corrosion protection coating and possible aerated concrete residues are not removed, the support rods would be coated with a further coating layer on renewed dipping in the corrosion protection medium bath, likewise the aerated concrete particles adhering to the rod. In this manner the coating on the support rods would become ever thicker. This has the consequence that the support rods can no longer be inserted from above through bores in the cross-pieces and also can no longer be withdrawn. Aerated concrete particles which adhere to the support rods and are fixed by a new coating would moreover form projections on the support rods, which make withdrawal from the hardened aerated concrete block difficult and can also lead to damage to the same during withdrawal. For these reasons the support rods must be cleaned after the withdrawal from the hardened aerated concrete block, which is very expensive and for which large quantities of solvent are necessary. Since these solvents are mostly a fire-risk, substantial protective measures are also necessary. Moreover the use of solvents is less friendly to the environment.
The desire for an environmentally friendly corrosion protection system has given the impetus to develop a water-lacquer, i.e. a water-thinned lacquer. This water-lacquer forms an irreversible film, i.e. once it has dried the corrosion protection coating can no longer be dissolved with water or solvents. Support rods, which are therefore dipped in a bath of water-lacquer together with the steel reinforcements hanging thereon can no longer be made lacquer-free with aid of solvents after drying of the water-lacquer.
In a known method of the initially mentioned kind (DE-OS 3 640 029) a water-based separating medium is applied to the support rods before applying the corrosion protection medium. This consists of 1.4 to 2.5 weight-% cellulose-glycol acid, 44 to 52.6 weight-% of an inert inorganic powder such as slate dust, talcum, kaolin, quartz powder, and 46 to 53.5 weight-% water. These components are stirred to a homogeneous mixture. The support rods are dipped in the separating medium consisting of these components. After the dipping the support rods retain a separating medium coating with a layer thickness of 250 to 350 .mu.m. Then the support rods with the steel reinforcements hanging thereon are provided with a lacquering, especially a powder lacquering. It is to be obtained through the separating layer that this adheres better to the powder mass than to the support rods, so that, on withdrawing the support rods, the coating of the support rods formed by the powder lacquer remains together with the separating layer in the aerated concrete.
Apart from the fact that it is not known if this separating medium can completely fulfil its function also with corrosion protection coatings consisting of a water-lacquer, the known separating medium has various disadvantages. There is not here in question a product customary in the trade but it must be separately made from the components mentioned above, for which weighing units, time and mixers are necessary. The drying of the relatively thick coating layer requires a long time or special, energy-expending drying apparatus. The relatively thick coating of 300 .mu.m on average can moreover be stripped off on pushing the support rods through the relatively narrow bores of the cross-piece or support frame and also on pushing into the spacers of the reinforcing mesh. Where the separating medium layer is stripped off there exists direct contact between the corrosion protection medium and the support rod. The corrosion protection medium will therefore stay adhered to the support rod at these places on withdrawal and at least a partial cleaning of the support rods is necessary. Furthermore the separating medium contains a high water content. This leads to corrosion of the support rods consisting of steel. The corroded (rusted) surface of the support rods is rough, so that on withdrawing the support rods from the aerated concrete block, at least part of the separating medium layer stays on the support rods. The same applies to such parts of the separating medium layer which lie at the upper ends of the support rods and are not sheathed with the corrosion protection medium when dipped therein. Aerated concrete residues can stay hanging here especially. In consequence at least a partial cleaning of the support rods is necessary in order to remove these residues.